Energy Dynamic Allocation Strategy of Distributed Energy Storage System Based on Virtual DC Machine

To enhance the inertia of the distributed energy storage system in the DC microgrid, and achieve the state of charge (abbr. SOC) balance of each energy storage unit(abbr. ESU) in the case of line impedance mismatch, a dynamic energy allocation strategy of distributed energy storage system based on virtual DC machine（abbr. VDCM）was proposed. Firstly, the VDCM technology was applied to the energy storage side control using the output characteristics of VDC to enhance the anti-interference capability of the system, then, using the output characteristics of the armature loop equation to dynamically design the virtual armature resistance according to the energy distribution demand of the energy storage system, so that it can adaptively change with the SOC within the specified limits, and the output power of each converter in real-time, and the voltage drop adjustment factor was introduced to dynamically fine-tune the virtual voltage drop of each converter to be equal, so as to compensate for the mismatch degree of the line impedance and realize the SOC equalization of each ESU. Secondly, a consensus algorithm was used to obtain the required average value information between adjacent ESUs, which improves the scalability of the system. Finally, a photovoltaic multi-energy storage DC microgrid system model was built, and the simulation and experimental results verify the rationality and effectiveness of the proposed control strategy.